Waste vegetable oil-based organic solvent for liquid-liquid extraction of methyl violet from aqueous solutions

The possibility of using two waste vegetable oil (residue oil from palm oil mill effluent (POME) and waste palm cooking oil (WPCO)) as a renewable and green organic solvent for methyl violet (MV) extraction from synthetic wastewater was investigated. Four factors (equilibrium pH, diluent. Di-2-ethylhexylphosphoric acid (D2EHPA) concentration, Tributylphosphate (TBP) concentration, and operating temperature) were screened by full factorial design. Central composite design (CCD) and response surface methodology (RSM) were used for optimisation study. Liquid-Liquid Extraction (LLE) results showed that equilibrium pH, carrier concentration, phase modifier concentration was significant. The optimum condition for using residue oil from POME as the organic solvent was: pH of 4.0, 124.92 mM of D2EHPA, 51.24 mM of TBP and operating temperature of 75˚C leading to extraction of 97.20% MV under the optimum condition. Slope analysis showed that one monomer of D2EHPA is attached to one MV molecule to form MV-D2EHPA complex.